This invention relates generally to integrated gasification combined-cycle (IGCC) power generation systems, and more specifically to methods and apparatus for decomposing waste gases in IGCC systems.
At least some known IGCC systems include a gasification system that is integrated with at least one power producing turbine system. For example, known gasifiers convert a mixture of fuel, air or oxygen, steam, and/or limestone into an output of partially combusted gas, sometimes referred to as “syngas”. The hot combustion gases are supplied to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
At least some known gasification processes generate flows of ammonia. For example, a small amount of byproduct ammonia is produced in the gasifier from organic nitrogen. In the hydrocarbon feed typically 5-15% of the organic nitrogen is converted to ammonia. This ammonia is then concentrated in the syngas condensate. The condensate is stripped and the ammonia rich vapor is sent to the reducing section of the claus boiler, in a sulfur recovery unit. However, some known bottoms gasification applications (e.g. oil field), sour gas reinjection is used instead of a sulfur unit. Additionally, other known applications use existing refinery sulfur units where integration of ammonia rich sour water stripper overhead may be problematic. Moreover, a direct oxidation sulfur recovery method does not include a high temperature furnace and thus would not be able to decompose ammonia.